Truck is done

[66chevy43]

Nice looking truck! good luck with gas mileage and with a 700r4 it should be better than that!

[MikeS.]

Sweet truck, good job!

[Clyde65]

I would second some of the ideas here. I think the rear is too low, if you have a 12 bolt, then you can only go to a 3.73 ( 4 series rear), which may only help a little. Beak in on the motor wont help but a little also, I am not sure the stall would or could be an issue.

I really like you truck, you did a fantastic job on her!!!

[chuckmc8]

Like Clyde said, 3:73 is the gear for 700R4. make sure your converter lock up is working correctly. IMO you should be seeing around 12 mpg

[ambros]

Thank you, I think I will go with the 3.73 gears it is 10 bolt rear end. Do you guys have an idea what the cost would be if I do the work myself

[kieth]

Originally Posted by ambros

Attachment 1231903 My 1965 C10 is finished ground up 8 months start to finish. I want to thank every one on the board. I learned so many things that saved me time and money. Now my only problem with the truck is gas mileage. I have a rebuilt 74 350 with a quadrajet carb 450/224-110 cam and a 700r4 trans. On my second tank of gas I got 6 mpg will this get better as the engine breaks in or do I change carbs and/or rear end gears

Changing over to taller gearing would help, before you spend all that money lets double check all specifications:

1. 350/quadro jet----? hp ?

2. transmission 700r4

3. current rear axle ratio 4:10

4. tire diameter ? what is the height of the rear tires from the ground to the top of the rear tire ?

after determining this diameter you can go to this link and see how your truck should perform......the key is torque within a usable range of speeds

we want to make sure your truck will pull taller gearing and that the truck is cruising at around 2000rpm at 65-68 mph with at least 460 ft lbs of torque...

Here is a link to spreadsheets that show you that information: go to post 6 or 7 there are file names with diameters in their name , click on the closest diameter and you can see which rear axle ratio you need.

http://6066gmcclub.com/forum/showthread.php?t=48090

[Clyde65]

Kieth,
the link wont let me in those PDF's without logging in...do I have to register and do all that??

[hddoc]

Very Nice !!!

[Robert Haas]

first off if you really do run a 2500 stall converter and go to a taller rear gear you will be in trouble. It works like this.

the R4 has an Overdrive and a taller gear, (3.73 to 1) will net a 60 MPH cruise RPM under the stall "lock" point on the converter. What this does is generate more heat and wear in the Transmission. R4's really prefer electrically locked converters for this very reason.

I would also self calibrate the actual speedometer error. Easily done then you will have a better level of accuracy to determine your true MPG.

Around town stop and go with a low gear and short tire with a Quadrajet can easily keep you under 8 MPG. However driving style has a huge effect on it.

[Bullett]

Ambros,

1 way to check exactly what your gear ratio is while running a certain height tire is to jack the rear of the truck up, with ignition off, put a mark at 12:00 on your rear tire, the n go under the truck and put a mark at dead bottom center of your drive shaft. then have someone slowly turn the tire exactly one rotation while you are under the truck counting how many revolutions the drive shaft makes. ex: if the tire is turned exactly one rotation and your drive shaft turns, say a little more than 4 times, I would equate that to roughly a 4:11 gear ratio. I believe this to be quite accurate but someone correct me if this isnt. I didnt read through all the posts, maybe someone else has suggested this?....Bullett

[ambros]

Tires are 29 inch high I will talk to the guy who helped me with the transmission exactly what the stall converter is

[Roll'nSlo]

Nice ride!!!!

[JWheeler331]

Looks great.

[ChevyFreak60]

Beautiful truck.....

[gimmy 64]

very nice truck. the motor is new so mileage may vary.lol my 64 gmc with 350 --2004r tranny 3:54 gears and a mild 1800 stall converter gets 14. mpgs at 72 mph turning 2100 rpms.

[ambros]

Thank you, I think we may have gotten it solved it does have an 1800 stall we had a problem with the cable and it was in overdrive just driving around town. I just drove it around and seems like a different truck.I will see on the next tank of gas where we stand

[C/10 King]

Nice truck, give yourself a pat on the back! Hope to see you and your truck at the "Brothers Show" on June 29!

[ambros]

I will try to make it it is real close to me